Ideal Protocols for the Restoration of Posterior Teeth

You're listening to The Dr. Phil Klein Dental Podcast from Viva Learning.com. Welcome to the show. I'm Dr. Phil Klein. Today we'll be discussing clinical strategies related to procedures that we do every day in our practice. This includes bonding zirconia crowns, layering composites, creating a composite crown, and throughout all of this, maximizing adhesive bond strength. Our guest is Dr. Clarence Tam, a multifaceted dentist with extensive knowledge and experience in restorative dentistry. Dr. Tam sits on the advisory board for Dental Asia and is part of the restorative advisory panel for Henry Schein Dental in New Zealand. Dr. Tam, it's a pleasure to have you on Dental Talk. Phil, thanks for having me. What a privilege to be here. Yeah, we're really happy to have you. Are you in New Zealand now? Yes, sir. I'm in Auckland. It's early in the morning. What time is it there? Not too early, 7 a.m. I'm already set up and done my pre-notes for my patients. We're ready to rock, yeah. Wow, that's great. So thank you for the time difference accommodation because then I know that is difficult. You're on the other side of the world. You're welcome to have me on the show at this time. Yeah. So let's begin with something that's really trendy right now. Zirconia crowns are like the in thing and they're taking over the market. So let's ask you, when it comes to zirconia crowns, can we take advantage of adhesive dentistry? And if so, what is the ideal bonding protocol? Right. Zirconia has its strengths and limitations. Of course, as we know, the higher the cubic nature of zirconia, the more translucent it is. Cubic zirconia being obviously fake diamonds. So if you really want to not impress your future wife, go and grab one of those guys. But if they do an electrical... or static test on that, you know, you're in big trouble. There are limitations with zirconia. I mean, zirconia is great for frameworks and kind of like, you know, more, I guess, like flexural strength requiring restorations. However, I find that if you're looking to zirconia for aesthetics, you're like, ooh, let's just do zirconia because it's actually, you know, stronger. It's actually not stronger than Emax. It's not stronger than lissy or lithium bisilicate in the anterior sextant. especially from a flexural strength standpoint when you're going for aesthetics. And in that situation, because even though you're trying to adhesively bond to zirconia, I'd rather choose something you can definitively bond to, and that is silicate ceramics. So in single unit cases, or maybe even now cantilever single unit anterior situations, I would choose bonded lithium disilicate instead of zirconia. But let's just say you've got this real fetish for zirconia. And you're like, well, let's try to bond this. As you know, it's like a non-polar oxide surface. So it's historically really, really hard to bond to. And so you're thinking, do I need mechanical retention form? A little bit is, of course, really, really nice to have that in your abutment tooth if you have. But definitely what you want to do is you want to increase the surface area of your zirconia or the... surface energy as well. And how you do that is use micro air abrasion. So the grit that I use is 27 micron aluminum oxide. And the reason I use 27 instead of 50 is because you want to simplify your protocols in clinical dentistry. You don't want to have like everything around. 50 is wicked for enamel, the integrative surface of your PFM crowns, even zirconia. But if you have any dentin exposed, 50 has six times the kinetic energy. of 27 micron aluminum oxide it's a bigger asteroid and it's going to destroy four times more collagen fibrils so that's why for clinical use i'm using 27 and you want to blast or you want to you know abrade the antagonist surface of your retainer or your crown for um with two to three bar or 30 to 40 psi of pressure and in so doing you're going to increase the surface energy for your next step. So obviously the first step is A, the second step is P, the third step is C. So we talked about A, which stands for abrasion. P stands for primer, and you're thinking, should I just use a silane? Well, no, not a silane, because silane is just 10 MPS, and MPS bonds from silica to a methyl group or a methyl group in resin. So we want to be using MDP. MDP is an acidic monomer. um with a phosphate group on one end and a hydroxyl group on the other and the phosphate group is the active situation here and it's been found to have a really good affinity for um zirconia as well as hydroxyapatite the collagen fibril non-precious metals the list goes on mdp Yeah, that's MDP. So that's what you find in Z Prime. That's what you find in, you know, Clear Fill Ceramic Primer, GC's G Multi Primer and stuff like that. So those are kind of my top three products for kind of an MDP containing primer. And what's interesting is just like Bond, you know how we scrub Bond for 30 seconds, you know, or a long time. We dip multiple times when you're scrubbing an indentin. You know, just really infiltrated between those collagen fibros that you hope you haven't desiccated. So the answer is you can bond, but there's these considerations of good surface preparation that you described here. But it sounds like to me you're not a major fan of zirconia just because everybody else is jumping on the bandwagon. And lithium disilicate, in your opinion, and elaborate on this if you would, Dr. Tam, serves us very well aesthetically. We have a long track record with it. And we also find that in most posterior cases, lithium disilicate is strong enough to do fine and you can bond to it. Is that how you look at it? Absolutely. On second molars, my go-to is lithium disilicate simply because you're able to be more conservative. I mean, you need to have a more traditional retentive. um a preparation form for zirconia and so i'm not so much a fan of that i mean you know like marcus blatz talks about defects above the equator and below and it's only below that you kind of need to have kind of a heavy chamfer or a chamfer um but if it's If there's no defect on the equator, on the facial, for example, then you can just have like a gradual chamfer, like a gradual bevel in that area. You can preserve a bunch of tooth structure. Whereas I wouldn't necessarily use that design and say, hey, look, I'm going to use my zirconia because it's going to bond really effectively there. I mean, you know, like the bond strength of zirconia is roughly around maybe 10 megapascals or so. So 10 to 18 at most. And I'm not super pleased with that. I mean, when we know that in these days, bonding technology, we're able to get bond strengths that pretty much approximate the tensile strength of enamel to dent in nature, which is 51.5 megapascals. So it's pretty cool where things are. Would you say that zirconia would be a good option, though, for someone who's a clencher? Brooks or someone who really has strong occlusal forces? Phil, that's a great question. I mean, zirconia, actually, despite its amazing flexural strength, it actually is nicer from a wear -resistant standpoint to human enamel relative to Emax. Emax, or lithium disilicate, is actually harsher. So if you kind of grind a lot and you're able to kind of remove the glaze off your Emax lookout, because that thing is going to be a force. Right. So let's talk about direct restoratives a little bit. Converting. I know in your lectures and you're going to be doing a lecture with us coming up. What is the ideal way to convert a class two into a class one? What kind of layering approach would you use for that? Yeah, that's a great question. I mean, typically, of course, there's a lot of people that kind of get on their garrison or triadent or paladent or, you know, there's, you know, bio clear matrices. they start building up the marginal ridge and stuff and they might leave the whole contraption on to kind of build their occlusal as well. And I find an issue with that because let's just say there's something wrong. You missed a bit of your, your, you know, like. your contact point is irregular, then you would have, then you have to prep back into that whole thing. And as you know, I love occlusal anatomy. So imagine if you have to blow back into that occlusal anatomy, it's a bad day. It's a bad day. Whereas if you just build up your marginal ridge, take off your contraption, you've got more visual and mechanical access to do your sexy class one. You're going to check your contact and your contact, if it's strong. amazing if it's garbage then you're going to you haven't expended any time on building the occlusal surface and you can wipe away that marginal origin you can start again but there is a sequence in dental school we learned oblique layering and we're in the lecture we're going to go through you know you know like a study that goes through different layering techniques and the resultant shear bond strength such as vertical layering what if we were to kind of minimize c factor influences further and actually layer vertically not obliquely because obliquely touches a bunch of walls even if we're kind of doing one little increments up there it's touching a bunch of walls what if we were to do vertical that's got a smaller footprint at least on one of the walls is that going to give you a higher bond strength what about horizontal straight across you know what about bulk fills because we talk about that and one thing that Junyi Tagami. So you know how we all have idols, right? I don't know who your idol is, but like in the world of dentistry, this Japanese guy, Junyi Tagami, he's like the man, right? One of his most famous quotes is, use bulk fills, not like bulk fills. Bulk fill composites are amazing in the sense that they have greater monomer conversion. They got amazing chameleon effects. Like they're supercharged, super composites, you know? But if you use them irresponsibly, Some of his optical coherence tomography studies shows that it can rip the composite from the base of your floor, and that's where you actually get post-op sensitivity. So we'll talk about layering protocols to actually minimize that from happening because you don't want that kind of call coming in. Does using a flowable down below in the first millimeter and then going with the bulk fill, does that help with that problem? Absolutely. Especially, and I think the buzzword these days is shrinkage stress. Not so much, hey, how much volumetric polymerization, contraction have you got? It's actually, how low is your stress? And that's why bulk fills are great too, because they have lower shrinkage stress. So I would say the most important thing is to really respect that first layer. Because one of the things I'll talk about, okay, let me ask you this. Let me ask you this. Let's just say we use a bond, really popular here in Australia and New Zealand, called GC's G Premium Bond. Okay, so you're following the whole protocol, blah, blah, blah, that we'll talk about. And then Phil decides to scrub it in, scrub it in, scrub it in, air thin, and hit it with the light. You cured it, right? Did you cure it? Is the bond cured? Is it, Phil? How do we know for sure? How do we know for sure, right? If not, why? Film thickness is 3 microns. How thick is the oxygen inhibition layer? 15 microns. Uh-oh. You've cured it. Actually, you've done nothing. Right. So let's just slam a bulk fill on there right now, and you link dentin to enamel. Bad news, because what's it going to bond stronger to? The more mineralized substrate, enamel. Where's it going to rip? Coronally. So there's all these considerations. How do we super strength? How do we maximize that hybridization of the dentin and make it as strong as can be, that bond strength, before loading it? And you can use bulk fills, but we want to make sure it's strong first before loading it. Right, no, that's a very good point. You know, a lot of dentists... very busy with their practice. They don't have the in-depth knowledge that obviously you have with getting down into the chemistry and the functionality of how these bonding agents work and the interaction between the materials. And that's a whole other science in itself. It's kind of like a material science sector of dentistry. But it's really interesting to hear your input and it's really important for dentists to stay up on continued education. I think your webinar coming up on Viva Learning is what, September 1st? Does that sound right? Yes, sir. Okay. So if you want to hear more from Dr. Tam, we're not done with this podcast yet, but I do want to make sure that you tune into her podcast coming up on September 1st and you can find her on vivalearning.com. Just type in TAM in the search bar and you'll find her upcoming webinar on September 1st. So what is the ideal protocol for maximizing adhesive bond strength? And let me ask you this also as a secondary part of this question. Is it important to stay within a company's product line using their bonding system, their composite and so forth. So you're staying within a system. So you know for sure that you're ruling out any, you know, things that don't... Incompatibilities or something like that. Yeah, incompatibilities. That's the word I'm looking for. Yes. What's your response to that? My take is basically composite chemistry is kind of the same from company to company. You're right. The likes of GC have got like no BIS -GMA in their product. They used to have stick resin, which is that dipping bond that was pure BIS -GMA. but now they switched it to modeling liquid and that's teg dma which is what we find in gmg icon so i mean if people are kind of like you know i really don't like this phenol a and stuff like that you can give them a gc range of products for example that's like you know um the best gma free if you will but personally i'm mixing match i don't know if you follow me on social i use the best material for that particular situation so i might start with for example a kerbond you know and then after the kerbond i might use a karari flowable and not one with the greatest shrinkage stress but one with the most amazing handling for me because there's another demon of mine as i like checking postoperatively to make sure i've got no bubbles bubbles are my nemesis i'll come to the practice at 2 a.m to check radiographs just because i think i saw a bubble in my post-op or something because i'm pretty crazy i'm not exactly normal so um so so after that i might be like the base is too dark i still see the stain denton floor i'm going to switch to ker ker herculite xl2 flowable xl2 or i might actually you know use vocos final touch white because that's composite tint as well because tints give you the most bang for your buck in terms of neutralization of color using the least amount of space And then for the occlusal, I might use, for example, Voco Grand EOSO, which is a supercomposite that I love using. So you can mix and match, but as long as the bonding chemistry is the same, then even within the Voco range, they have a composite called Admira Fusion. Have you heard of that before? Yes, yes. Yeah, tell us about Admira Fusion, because I've heard a lot about that, and a lot of KOLs are using it. What's special about that? It's special because it actually doesn't have any BIS-GMA at all. so we talked about like you know like for more holistic patients you don't want this gma they might not realize that okay well you can get bonds without this gma all right just like gc's bond that i talk about and stuff like i take gma but no bis gma and um it's an organically modified ceramic so this composite is made up of tons of silica particles usually it's silica in a sea of bis GMA, if you will, right? Or a resin matrix. And in this situation, you've got tons of silica particles, each modified with little methyl groups sticking out of it like a virus, if you will. And those methyl groups are not only able to kind of cross-link to each other, right? They're so dense that when they cross-link to each other, you know, there's no real shrinkage. It was very, very low. I think it was 1.25% polymerization contraction. But also, the methyl group allows it to... to regular bonds. So you might have used Kerr Optibond Solo Plus or Kerr Optibond FL for that bonding layer and stuff like that, but it's able to adhere to that. So that is an all ceramic composite. It's interesting. It's almost like a new category of direct restoratives and the feedback and the research coming back from Admira Fusion has been really, really good. To switch gears a bit, tell us about the chair side composite crown. well pretty much with the chair side composite crown but use it in situations where you've got a multi-surface restoration where you feel like, you know, you wouldn't have the direct access or patient compliance to complete the restoration. You know, obviously on a young individual, you know, person with hypomineralization or hypoplasia. you know, those situations call for it. Like if you had a nine-year-old in the chair or something like that, or if you had like a 13-year-old, if you don't have Netflix, God help you, you know, because, you know, they're going to be twisted to the left and right. And are you done yet? And you're like, whoa, whoa, what color do I use? Oh, wait, wait. You know, did Clary say start on a mesial buckle cusp? Oh, wait, but I'm missing that. Like, did I take a pre-op putty matrix? So all of these things will be discussed, but pretty much what we're doing is we're going to... like, we're going to get to a Denton base that we're happy with or a situation that we're happy with. And then we're going to take an impression of that, not with the PVS or not with the, you know, a condensation or addition silicone, because that's going to bond to our model material, which is not out of stone this time. It's also out of addition silicone. So if you take an addition silicone impression and you pour it up in a silicone as well, you're going to stick together. It's not good. So this is one of the times where for a crown or for an indirect, you're going to use them. you're going to use just regular alginate and an alginate you're going to pour it up with that boco a silicone that dye silicone material and in a matter of minutes it sets hard but this material is cool number one it's red number two it flexes a little bit as well so if you have restorations on there and you want to get it off it's not totally rigid you're able to to flex it off finish it put it back on and then you can try it in the mouth which is really really cool so i'll go through the layering protocol for that during the lecture you're building it up direct extra orally And in so doing, you're able to get maximal polymerization, you know, contraction, monomer conversion. You're able to cure it properties wise. That restoration is going to be better. It's going to be more stain resistant. You're going to have better control of the anatomy, et cetera, as opposed to trying to do something heroic in a patient's mouth. And the patient can watch you and, you know, and you might have to, you know, top up their anesthetic a little bit, you know, but it's a nicer experience for everybody overall and allows you a greater degree of satisfaction and control. And how long does that procedure take to make this composite crown? I did two teeth for, I think, a 13-year-old. And I think it roughly took me around two, two and a half hours or so. But you're charging for that. I mean, you can if you're like super fast, just like blitz through it and kind of do something fast and dirty. But you'll see pretty much I put my heart and soul in every single case. And you'll see the anatomy is reflective of that. And that's a one-visit deal. Right. They come in and they walk out with two beautiful crowns that are composite made chair side. Exactly. What's the longevity, expected longevity of something like that? Well, in the literature, of course, you know, composite last seven years. But I mean, we're seeing with the likes of Voco Grande USO at the nine year mark, because I bought this particular practice here in Newmarket Auckland nine years ago. They look exactly the same as the day I put them in. The margins, amazing, like the color integrity. Awesome. There's no indication to even think about replacing those restorations. So imagine if you had like something that didn't have that polymerization contraction consideration intraorally, and you polymerize that extraorally, and then you cement that in a conventional way, not conventional, in an adhesive conventional way. That should last you pretty much, I mean, as long as they don't break it. I mean, in Boco Grandioso, it's like, you know, flexural strength is higher than natural dentin. It's incredible. These new composite materials. have properties in some categories that exceed that of nature. So the realm of bionic teeth may be here. It sounds like you're a real adventurist when it comes to doing, you're not afraid to try new things in your office and also lead the way. You're kind of a leader when it comes to breaking the path for new ways of doing things. So that's interesting. You're also not one to follow the pack just because everybody's moving towards zirconia. Many dentists are moving towards zirconia. You're still fine. And I do hear that from a lot of other key opinion leaders and thought leaders that lithium disilicate is still their go-to and they're not changing because of all the advantages that that material brings to the table. By the way, do you do any chair-side milling in your practice? I used to, but I didn't like the aesthetics of it, as you can imagine. And I like pressed as opposed to that, so I work with my ceramist. So my practice is really clean. There's no printers, no millers and stuff like that. We don't have resin vats lying around. If I want something, I'll set it off and they'll send back the model and the appliance completely done. It's quite nice. You focus on the clinical aspects of dentistry and not so much lab work. What about a digital scanner? Yeah, yeah. We've got a prime scan here. Okay. So you use a digital scanner, but you rely on the lab and you don't design your own restorations chair side. You let the lab design it? I do. I do. And I give them direction as such. I mean, if you've got like a number five or something like that, you'll be like, oh, you know, can I tell you the ideal anatomy for this? No one's going to listen to you and they'll probably fire you as client. You know, they'll be like, whoa, this guy's intense. When it comes down to it, I think there'll be a percentage, a smaller percentage of dentists that do it all. They'll have the scanner. They have all the design software, they mill it, and they become their own lab. But for the most part, I think dentists are going to be going along your path where they're continuing to do clinical dentistry and relying on the lab for what they do best. I don't think the labs are going anywhere. Let's just say that if I was living in the sticks or the boondocks, I probably would have a miller and all that kind of stuff because then I could control everything. I wouldn't say, oh, the courier is going to come in two weeks' time. Oh, sorry. then I'm doing everything myself and I'm controlling everything. And I probably get really, really good at it. It's not to say that, you know, you know, CEREC or it's like, is that or anything like that? It takes a certain learning curve or workflow. And the more you do it, as with anything, with a focus on perfect practice, you can get amazing at it. You know, and my mentor, Graham Milicich, and of course, like, you know, there's so many people, as you know, that are absolutely stars at it, like James Clem and everything like that. I mean, like, absolutely. Incredible clinicians. So everybody's got their own style. Everyone's got their like phobias and philias, if you will. And yeah, I mean, there is a time for digital. I mean, like I believe in like the hand sculpted aesthetics that the Europeans do and like Nelson Rego and stuff at the AACD, et cetera. So much that during COVID, I invented a mixing deck for feldspathic porcelain that is a rotating table with a tooth shape. And I won a design award here in New Zealand. That's pretty wicked. I got it patented. Amazing. Yeah, it's wicked. So, I mean, that handheld, you know, even if you're doing Emacs, you know, you're still cutting back at least the incisal third and you're doing some micro layering just to infuse that sex appeal. That's really important. Talking to Clary Tam from New Zealand, when we started this podcast, it was 7 a.m. Now it's probably about 7.25. You're starting your patients soon, but we really do appreciate your time. You've got incredible energy, enthusiasm, you know. ton of stuff. It was difficult for me to follow all this stuff, but I'm a retired endodontist. So what do I know? But yeah, but basically it's been very interesting to talk to you. And again, September 1st, we're looking forward to seeing some slides and your presentation and all your innovation that you bring to the table. And we're happy that you shared it with us. Thank you so much, Dr. Tam. Thank you so much. Thank you. Have a great day.